The envelope of lighting devices may be filled with a thermally conducting gas so as to provide cooling of light sources, such as e.g. light emitting diodes (LEDs), arranged within the envelope. One drawback with such technologies is however that the light source may age prematurely due to by-products and contaminants from e.g. the light source, which are released within the enclosure and may deposit on e.g. light emitting portions of the light source. As the light source is gradually obscured by the deposited contaminants, performance of the light source may degrade in terms of e.g. colour distribution and light intensity.
WO 2013/154932 addresses this issue by including oxygen in the enclosure, since oxygen has been discovered to lower or eliminate the contaminants. It is however difficult to determine a suitable amount of oxygen, since too high concentrations of oxygen may reduce the cooling performance of the lighting device and too low concentrations may not be sufficient to reduce or eliminate the contaminants.
Hence, there is a need for improved lighting devices which are capable of reducing contamination and degradation of the light source. There is also a need for lighting devices having an increased life.